Method for analyzing a mixture of biological and/or chemical components using magnetic particles and device for the implementation of said method

ABSTRACT

Disclosed is a method of analysis of a mixture of biological and/or chemical components that entails spatially arranging a chosen component attached to magnetic particles, exposing the particles to a magnetic field, and recording a magnetic induction signal, from which the content of the analyte in the mixture is judged; this includes grouping the chosen component in a probe volume, making the magnetic field alternating, pre-setting its spectrum, at least, at two frequencies, and recording the signal at a frequency, which is a linear combination of these frequencies, during the exposure of the magnetic particles to the field.

TECHNICAL FIELD

The proposed method refers to the field of development and improvementof means for biochemical analyses and to the field of chemical andbio-sensors.

BACKGROUND ART

A method of biochemical analysis of a mixture of components with the useof magnetic particles is known [Ch. B. Kriz, K. Radevik, D. Kriz,Magnetic Permeability Measurements in Bioanalysis and Biosensors/Anal.Chem. 68, 1996, pp. 1966-1970], which includes the following:

-   -   making use of a chosen component attached to magnetic particles;    -   exposing said magnetic particles to a magnetic field,    -   recording a signal due to the magnetic induction produced by        said magnetic particles as a result of their exposure to the        magnetic field,    -   judging the content of the analyte in the mixture being analysed        from the value of said signal.

According to this method, one introduces particles into a specimen ofthe mixture to be analysed, which particles carry recognising elementsthat selectively bind the analyte. Besides, in the mixture beinganalysed there should be a chosen component attached to magneticparticles. This component binds selectively to the analyte after bindingof the latter to the recognising elements, or competes with the analytefor binding to the recognising elements. In exceptional cases when theanalyte contains magnetic particles, the chosen component can be theanalyte itself.

As this takes place, this method necessarily includes removing from thespecimen such magnetic particles that have appeared to be unbound to thecarrier particles after the course of the reactions mentioned above. Todo so, the specimen is subjected to sedimentation, spinning, and rinsingwith a binding buffer solution. Then a certain dose of the specimen isplaced in a test-tube, which is inserted in an inductance coil. From thechange of the magnetic induction of the coil after inserting thespecimen into it the content of the analyte in the medium being analysedis judged.

The drawback of this analogue consists in its high complexity and lowthroughput because of a large number of operations. This leads also tohigh cost, insufficient reliability and low accuracy of the resultsobtained.

The closest to the proposed method is an analogue-method ofpolynucleotide and protein analysis using magnetisable moieties [U.S.Pat. No. 5,656,429 of Dec. 8, 1997, Polynucleotide and protein analysismethod using magnetizable moieties, Int. Cl .: C12 Q1/68, U.S. Cl.:435/6,], which comprises the following operations:

-   -   choosing a component for attaching magnetic particles to it or a        component that is already attached to magnetic particles, this        chosen component being either the analyte or another component        that allows judging the content of the analyte in the mixture        being analysed,    -   spatially arranging said chosen component,    -   attaching magnetic particles to said chosen component or using        said chosen component that is already attached to magnetic        particles,    -   exposing said magnetic particles to a magnetic field,    -   recording a signal due to the magnetic induction produced by        said magnetic particles as a result of their exposure to the        magnetic field,    -   judging the content of the analyte in the mixture being analysed        from the value of said signal.

In doing so, one distributes components in a prescribed manner (e.g., byelectrophoresis) on the surface of a substrate according to themolecular size and the quantity of the components in the mixture beinganalysed. Magnetic particles are attached to one or another component ofthe mixture before or after distributing the components on the substratesurface. Then one records the resulting distribution by magnetic readingfrom the substrate surface similarly to that one reads information froma magnetic disk. From said distribution one obtains information on thecontent of one or another component in the mixture being analysed. Toenable the magnetic reading, the particles are magnetised by a dcmagnetic field before or after distributing them on the substratesurface. The magnetic reading itself consists in the measurement of themagnetic induction resulting from the residual magnetisation of theparticles. An important merit of the analogue-method is the spatialarranging of magnetic particles that are bound with the analyte or thechosen component. This arranging takes place on the substrate surface ina close proximity to a magnetic reader. Consequently, the reliability ofthe results is increased, the dimensions of the required apparatus areminimised, and compatibility of the apparatus with microelectronicstechnologies is ensured.

The drawbacks of this analogue-method are low sensitivity of the methodand low accuracy of the results it yields, due to a number of reasons.These are: first, small concentration of the magnetic particles beingrecorded, which are “spread” on the substrate surface; second, verysmall residual magnetisation of known particles of micron and submicronsize; and, third, well-known negative features of dc measurements. Thementioned reasons result in narrow application area of this method.

An analogue-apparatus for reading results is known for the method ofbiochemical analysis of a mixture of substances, using magnetic labels[Ch. B. Kriz, K. Radevik, D. Kriz, Magnetic Permeability Measurements inBioanalysis and Biosensors/Anal. Chem. 68, 1996, pp. 1966-1970], whichcomprises:

-   -   magnetic particles attached to a chosen component of the mixture        being analysed, directly or through an intermediate material;    -   a magnetic field generator, within which action said magnetic        particles are situated;    -   a meter of the magnetic induction produced by said magnetic        particles;    -   an output signal receiver;    -   a block generating the result, which input is connected to the        output of the output signal receiver.

In this apparatus the magnetic induction meter, which is made as aninductance coil, is inserted in one arm of a bridge circuit, which inputis connected to the output of the magnetic field generator and the inputof the circuit is connected to the input of the output signal receiver.

The operation of this analogue-apparatus relies upon that the presenceof magnetic particles in the sample being analysed and situated insidethe inductance coil, which serves as the magnetic induction meter, leadsto a change in this inductance and, hence, to a misbalance of the bridgecircuit. This causes the generation of the output signal of thediscussed apparatus.

The drawbacks of this analogue-apparatus are its high complexity and lowthroughput because the bridge should be precisely balanced for each newmeasurement. This also leads to high cost and, taking into accountenvironmental temperature instabilities (especially in portable variantsof the apparatus), to low accuracy of the results obtained.

The closest to the proposed apparatus is analogue-apparatus used forinformation reading in the polynucleotide and protein analysis methodusing magnetisable moieties [U.S. Pat. No. 5,656,429 of Dec. 8, 1997,Polynucleotide and protein analysis method using magnetizable moieties,Int. Cl.: C12Q 1/68, U.S. Cl.: 435/6], which comprises:

-   -   a chosen component of the mixture being analysed, said component        being spatially arranged in a prescribed manner;    -   magnetic particles attached to the chosen component of the        mixture being analysed directly or through an intermediate        material;    -   a magnetic field generator, within which action said magnetic        particles are situated;    -   a meter of the magnetic induction produced by said magnetic        particles;    -   an output signal receiver;    -   a block generating the result, which input is connected to the        output of the output signal receiver.

Besides, the components of the mixture being analysed are distributed onthe surface of a substrate according to their molecular size, themagnetic field generator and the magnetic induction meter enablegeneration and, respectively, recording of a signal constant in time.

The operation of the analogue-apparatus relies upon that the magneticparticles attached to one or several chosen components of the mixturebeing analysed, and distributed along the substrate surface, acquire aresidual magnetisation resulting from their exposure to a dc magneticfield. Then by means of a dc magnetic field meter, e.g., a Hall sensor,one records the distribution of the magnetic induction caused by theresidual magnetisation on the substrate surface. From this distributionone determines the amount of magnetic particles attached to one oranother component of the mixture being analysed, and the content of thiscomponent in the mixture.

The drawbacks of this analogue are limited sensitivity of the apparatusand low accuracy of the results obtained. These are due to knownnegative features of dc measurements, low value of residualmagnetisation, and low concentration of magnetic particles, which arespread on the surface of a substrate. The application area of thisapparatus is rather narrow, too.

To conclude, the wanted technical result consists in risingsignal-to-noise ratio and, hence, increasing measurement accuracy,enhancing sensitivity of the method and apparatus, improving reliabilityof the data obtained, along with lowering the costs of experiments owingto reduction of the operation number and time needed, amount anddimensions of the apparatus, and, besides, in developing mobile, cheap,high-throughput laboratories for mass tests, in improving theoperational flexibility of the method and apparatus and extending theirapplication area.

DISCLOSURE OF INVENTION

To achieve the mentioned technical result, there is proposed a method ofanalysis of a mixture of biological and/or chemical components with theuse of magnetic particles, which comprises:

-   -   choosing a component for attaching magnetic particles to it or a        component that is already attached to magnetic particles, this        chosen component being either the analyte or another component        that allows judging the content of the analyte in the mixture        being analysed,    -   spatially arranging said chosen component,    -   attaching magnetic particles to said chosen component or using        said chosen component that is already attached to magnetic        particles,    -   exposing said magnetic particles to a magnetic field,    -   recording a signal due to the magnetic induction produced by        said magnetic particles as a result of their exposure to the        magnetic field,    -   judging the content of the analyte in the mixture being analysed        from the value of said signal, similarly to the analogue-method.

The proposed method differs in that:

-   -   spatially arranging said chosen component includes grouping this        component in a probe volume;    -   said magnetic field is alternating, and its spectrum is pre-set        with spectral components, at least, at two frequencies;    -   said signal is being recorded at such a frequency that is a        linear combination of the frequencies of said spectral        components, during the exposure of said magnetic particles to        said magnetic field.

Besides, said linear combination of the frequencies of said spectralcomponents is the sum or the difference of these frequencies.

Besides, the amplitude of, at least, one of said spectral components ischosen high enough to ensure a non-linear dependence of said magneticinduction on the strength of said magnetic field.

Besides, the amplitudes A_(h) and A_(l) of said spectral components,which pertain to the higher and the lower frequencies, respectively, arechosen according to the relationship A_(l)/A_(h)>2.

Besides, the magnetic field strength vectors pertaining to, at least,two said spectral components, are oriented non-collinear to each other.

Besides, the magnetic particles are made of a soft magnetic material.

Besides, in said probe volume a working surface is formed, and saidchosen component is being spatially arranged through binding thiscomponent to the working surface.

Besides, the working surface is formed through filling the probe volumewith micro-granules.

Besides, said micro-granules are made of polyethylene.

Besides, said micro-granules are made under low pressure frompolyethylene stabilised with gamma-radiation.

Besides, the working surface is formed through filling the probe volumewith a capillary-porous structure.

Besides, the working surface is formed with immobilising a reagent onit, which is capable of binding the analyte in a selective manner, andthrough this reagent said chosen component is being bound to the workingsurface.

Besides, said probe volume is formed from several spatially separatedregions, and the possibility to record said signal is ensured for eachof said regions.

Besides, in said regions a working surface is formed and on this workingsurface various reagents are immobilised, which are capable of bindingvarious analytes selectively and through which chosen components arebeing bound to the working surface, from recording said signal for eachof several said regions the information on the contents of severalanalytes in the mixture being analysed is being obtained.

One of the distinctive features of the proposed method consists in thatthe spatial arranging of the chosen component of the mixture beinganalysed with magnetic particles attached to it is accompanied by thegrouping of this component in a probe volume. This leads to asubstantial increase of the concentration of the magnetic particlesbeing recorded in the region of their exposure to the magnetic field andin close proximity to the magnetic induction meter. This, in turn,results in a drastic increase of the signal being measured against thenoise level. The grouping in the probe volume can be done using severalapproaches. Among them, there are biological or chemical binding as wellas adsorption or absorption of particles or molecules of the chosencomponent in a pre-set spatial region or a number of such regions.Besides, said grouping can be performed through exposure to aninhomogeneous magnetic field, filtration, sedimentation, etc. In anumber of cases the grouping can take place near a surface, which isalready present in the control volume, or near an intentionally formedworking surface. The variants of forming the working surfaceparticularly include chemical modification of a surface present in thecontrol volume, immobilisation of one or another reagent on such asurface, and, besides, the synthesis of a biomolecular matrix or aspacer layer to realise such immobilisation in a two- orthree-dimensional region. Among the cases of said grouping, which arethe most important in practice, are reactions of selective binding(recognition) of the chosen component and a reagent complementary to it,which is immobilised in the probe volume, in particular, on the formedworking surface. The examples of such reactions are variousligand-receptor interactions, antigen-antibody and biotin-avidinbinding, etc., as well as binding of complementary DNA fragments (DNAhybridisation). Of good promise for practical applications is to carryout said grouping through selective binding on the large effectiveworking surface of a capillary or porous structure formed in a probevolume similar to a chromatography column or on the working surface ofwells of standard microtiter plates (e.g., arrays of 8×12, 16×24, 32×48wells), which are used in Enzyme-Linked Immuno-Sorbent Assays (ELISA)and other biochemical analyses with biochips.

In doing this, various approaches can be used to employ recognitionreactions for arranging the chosen component spatially and obtaininginformation on the analyte. Besides, there can be differentrelationships between the analyte and the chosen component. The chosencomponent can be either the analyte itself or another component, whichcontent in the probe volume enable one to judge directly or indirectlythe content of the analyte in the mixture being analysed.

In the simplest case the analyte itself possesses magnetic propertiesand contains magnetic particles (e.g., ferritin protein). The analyte inthis case serves simultaneously as the chosen component, which is beingspatially arranged through selective binding with a recognising reagent(e.g., an antibody specific to this protein). In other cases magneticparticles are being attached to the chosen component. Magnetic particlesare considered to mean particles that reveal magnetisation underexposure to an external magnetic field and, as a rule, are joined to amaterial (conjugate) that ensures their biological compatibility.

In another method (“sandwich assay”), the analyte also serves as thechosen component, and magnetic particles are attached to this componentin a selective manner, as a rule, before or after selective binding ofthis component with a recognising reagent. The attachment of themagnetic particles can be done, as the case requires, directly orthrough an intermediate material. In particular, it is the intermediatematerial previously joined to the magnetic particles that is advisableto use to ensure the selectivity of the attachment of the magneticparticles to the analyte. For example, one epitope of the analyte bindsselectively to a recognising material while another epitope does to saidintermediate material.

In a third method such a chosen component is used that, along with theanalyte, is capable of selective binding with a recognising reagent. Inthis case the chosen component competes with the analyte for binding tothe recognising reagent (“competitive assay”). Magnetic particles arebeing selectively attached to the chosen component, as a rule, before orafter its selective binding to the recognising reagent (in a similarmanner, directly or through an intermediate material). Otherwise, achosen component that is already attached to magnetic particles is used.In order to judge the quantity of the analyte in the mixture beinganalysed from the extent, to which the chosen competitive componentbinds to the recognising reagent, the mixture must contain a knownquantity of the chosen component prior to the analysis. Practically, aknown quantity of such a chosen component is usually introduced into themixture being analysed before the analysis.

In all mentioned modifications of the proposed method there exists aunambiguous relationship between the quantity of the magnetic particlesgrouped in a specified probe volume due to selective binding of a chosencomponent, and the sought-for content of the analyte in the mixturebeing analysed. One records a signal related to the magnetic inductionproduced by the particles as a result of their exposure to a magneticfield and then judges the quantity of the grouped magnetic particles andthe content of the analyte in the mixture.

From the foregoing it is seen that in the proposed method magneticparticles play the role of labels (markers) of a chosen component,similarly to how enzyme, fluorescent, radioactive, and other labels areused in conventional procedures of biochemical analyses.

In doing so, however, one uses an alternating magnetic field andpre-sets its spectrum with spectral components, at least, at twofrequencies, and records said signal at such frequency that is a linearcombination of the frequencies of said spectral components, during theexposure of said magnetic particles to said magnetic field. Thefrequency spectrum of the magnetic field acting on the magneticparticles is pre-set with due regard to the properties of the medium tobe analysed or a buffer medium, in particular, to specific bands orspectral regions of absorption of high-frequency electromagnetic fieldby such a medium. For example, when analysing biological solutions it isimportant to take into account the conductivity and the absorption ofwater in MHz and GHz ranges.

Measuring the signal during the exposure to the magnetic field isanother important distinction from the analogue-method. It enables oneto avoid relying on a residual magnetisation. One measures a signal at acombinatorial frequency. Hence one records a parameter relatedexclusively to the quantity of magnetic particles being detected ratherthan to the acting magnetic field or magnetic field-induced circuitryinterference at the frequency of the field or multiples of it. Ingeneral, such a combinatorial frequency is a linear combination offrequencies f₁ and f₂ as f₁=m f₁+n f₂, where m and n are positive ornegative integers other than zero, and f₁ and f₂ are, respectively, thegreater and the lesser frequency of two said spectral components of theacting magnetic field. In principle, said linear combination may alsoinclude a greater number of frequencies of spectral components of themagnetic field. Besides, the values of m and n may vary, as thesituation requires. For example, said linear combination may appear asf₁=f₁±f₂ (that is, be a sum or a difference of the frequencies of saidspectral components), f₁=f₁±2f₂, and so on.

It should be noted that, other conditions being equal, one can detectthe chosen component with magnetic particles attached to it frommeasurements of not only at a combinatorial frequency, but also at afrequency multiple to the frequency of the acting magnetic field (i.e.,at m=0 or n=0, or under exposure to a magnetic field of one frequencyonly). In the latter case, the magnetic induction signal measured at amultiple (i.e. double) frequency is also determined by the quantity ofthe magnetic particles being detected rather than by the amplitude ofthe acting field, since it is the material of the magnetic particlesthat introduces a non-linear dependence of the magnetic induction beingmeasured on the strength of the acting magnetic field. It is thisnon-linear dependence that results in combinatorial and multiplefrequencies in the spectrum of the magnetic induction signal. In theproposed method recording a signal at a combinatorial frequency is madeuse of as a preferred way to distinguish the informational signal fromnoise and circuit interference.

One may also use various relationships between the amplitudes of saidfrequency components of the magnetic field. The amplitude of, at least,one of said spectral components is chosen high enough to ensurenon-linear dependence of said magnetic induction on the strength of saidmagnetic field, because this is necessary for combinatorial frequenciesto appear. The quantitative measure of the non-linearity used depends onthe parameters of the employed circuit, which records the signal at acombinatorial frequency, and on the ability of this circuit todistinguish this signal from noisy background. Lowering the amplitude ofthe higher frequency component of the acting field spectrum is advisablefor realisation of linear regime of measurements of the signal formed,for simplicity of apparatus embodiments, and for lowering the energyconsumption. That is why the amplitudes A_(h) and A_(l) of said spectralcomponents, which pertain to the higher and the lower frequencies,respectively, are chosen according to the relationship A_(l)/A_(h)>2.

Thus, in actual practice, it is the lower frequency component of theacting magnetic field that usually provides the non-linear dependence ofthe magnetic induction produced by said magnetic particles on thestrength of the field. To enhance the signal at a combinatorialfrequency, the amplitude of said lower frequency component shouldcorrespond to the saturation of this dependence or, at least, to theregime close to saturation. This, of course, implies essentialnon-linearity. For the sake of simplicity one may say that the lowerfrequency component of the field periodically “switches” the mentionednon-linearity on and off. From experimental realisation of the proposedmethod it has been found that the amplitude of the lower frequencycomponent can be optimised using various optimisation criteria. Forexample, the maximum signal at a combinatorial frequency has beenobtained at such a value of the lower frequency component amplitude,that the saturation state takes place approximately for half time. Toincrease stability against external factors (temperature,electromagnetic interference, drifts, etc.), this amplitude isreasonable to choose somewhat higher.

Besides, the magnetic strength vectors pertaining to, at least, two saidspectral components, in a number of cases are oriented non-collinear toeach other. This is thought to be useful for rising the efficiency ofthe non-linear interaction between external signals and the system ofmagnetic particles, for example, when recording a spin echo signal.

The magnetic particles are made of a soft magnetic material in order toincrease the magnetic induction, which is the response of the magneticmaterial of the particles and on which directly the magnitude of themeasured signal depends. Besides, commercially available magneticparticles (“magnetic beads”), which are conventionally applied forbio-magnetic separation, can also be used. Usually these are supplied ascolloidal mixtures (“ferrofluids”). Such particles are, as a rule, fromtens nanometres to tens microns in size, contain a magnetic material(usually □Fe₂O₃, Fe₃O₄) in a polymeric entrapment, and aresuperparamagnetic. The latter term means that the particles revealmagnetic properties only when placed in an external magnetic field butdo not reveal residual magnetisation after being removed from thisfield.

To build up the most favourable conditions for grouping the chosencomponent in a probe volume and for localising this component in closeproximity to the magnetic induction meter, in said probe volume aworking surface is purpose formed, and said chosen component is beingspatially arranged through binding this component to the workingsurface. Preferable is the formation of a well-developed working surfacewith a high effective surface value in a three-dimensional region of theprobe volume or the synthesis of a three-dimensional bindingbiomolecular matrix (i.e., dextrane, peptide spacers, etc.) on one ofthe surfaces within the probe volume. This provides for a large numberof elementary events of selective binding (recognition) of an analyte ora chosen component per unit volume near the magnetic induction meter. Asa result, large number of magnetic particles localised near the magneticinduction meter and high level of information signal against noises areensured. The formation of the working surface may also include physicalor chemical treatment or modification of a surface (e.g., etching toprovide for binding of one or another reagent or to create a porousstructure), immobilisation of bio-reagents, etc., as already mentionedabove.

One of the variants of the working surface formation in a probe volumeconsists in that the probe volume is filled with micro-granules fully orpartially. This allows increasing the surface, on which the biochemicalreactions of interest occur. This, in turn, leads to the increase of theconcentration and the total number of the magnetic particles beinggrouped and, consequently, of the signal being measured.

Besides, said micro-granules are produced under low pressure frompolyethylene stabilised with gamma-radiation. This provides for highimmunity of the working surface to chemical and mechanical destructivefactors.

Another variant of working surface formation consists in filling theprobe volume with a capillary-porous structure fully or partially.Capillary or porous structure can be created in the probe volume throughplacing capillary or porous materials in it, or by other physical orchemical methods (e.g., etching, annealing, etc.). One of the preferredvariants of the proposed method consists in passing the mixture beinganalysed through a micro-column filled with a porous, filtering body,which has a very high value of effective internal surface. This surfaceserves as the working surface, at which a chosen component is beinggrouped, as a rule, through binding to a recognising reagent immobilisedon this surface. The creation of a capillary or a porous structure in aprobe volume provides for the increase of the surface, on whichbiochemical reactions occur, the quantity of magnetic particles beingrecorded and, consequently, the signal being measured.

To ensure selectivity of the analysis for the content of one or anotheranalyte, the working surface is formed with immobilising a reagent onit, which is capable of binding(recognising) the analyte in a selectivemanner, and through this reagent said chosen component is being bound tothe working surface.

To solve a number of practical problems, said probe volume is formedfrom several spatially separated regions, and the possibility to recordsaid signal is ensured for each of said regions. First of all, suchrecording of information signal for each of several channelsindependently allows using the channels for generation of referencesignals (i.e., reference channels) of various functions. For example, itis reasonable to exploit reference channels to compensate for probableoccasional errors, scatter of parameters, inhomogeneities of samples ofthe mixture, as well as non-specific (non-selective) grouping ofcomponents of the mixture being analysed in the probe volume, andnon-specific binding of the components to the working surface or to themagnetic particles. Besides, for repetitive analyses or continuousmonitoring, reference channels can serve to take into accounttemperature drifts and other physical or chemical instabilities (e.g.,pressure, density, pH of a solution or concentration of unwantedimpurities in it, etc.). In such applications, as a rule, a referencechannel is under the same conditions as an informative one, except forselective grouping of a chosen component (its binding to a recognisingreagent).

Another group of tasks, in which multiple-channel recording is required,relates to providing for high throughput of analyses. This is ofparticular importance, for example, for testing new preparations inpharmaceutical industry. For solving such problems it is reasonable, inparticular, to realise the proposed method on the basis of the currentELISA standards using sets of great number of reaction wells and, ofcourse, with the use of magnetic labels instead of enzyme ones.

A third group of the tasks is the recognition of complex multi-componentmixtures and their analysis for a number of components simultaneously.To do this, in said spatially separated regions a working surface isformed and on this working surface various reagents are immobilised,which are capable of binding various analytes selectively and throughwhich chosen components are being bound to the working surface, and fromrecording said signal for each of several said regions the informationon the contents of several analytes in the mixture being analysed isbeing obtained. In the simplest case, when the degree of selectivity ofthe binding of each chosen component with a respective recognisingreagent is high enough, each of said regions is associated with no morethan one such reagent and no more than one analyte; that is, one regionis “responsible” for the recognition of one component, and some regionsare used as reference channels. In other cases, from said regions acomplex signal pattern is obtained, each signal has a low specificity toone or another component, but the entire pattern appears specific (as afingerprint) to the mixture being analysed as a whole. In this case, themixture can be identified, for example, with computer methods of patternrecognition. Such approaches are known with no connection to theproposed method and are referred to as “biochips”, “gene chips”,electronic “nose” and “tongue” etc.

The mentioned variants of the method, with forming the probe volume and,respectively, the working surface consisting in a number of spatiallyseparated regions and providing for the recording of said signal foreach of said regions independently, are realised, for example, by theinteraction of the medium being analysed, or its parts, independently(in parallel) or successively with each of said regions. The variant ofthe parallel (not obligatory simultaneous) interaction is realised, forexample, by the interaction of the mixture as a whole with a biochip, agene chip, a chip for a combinatorial chemistry analysis, etc., or bydosing the portions of the mixture being analysed into titer platescontaining arrays of reaction cells (ELISA-like, etc.). The variant ofthe successive interaction is realised, for example, by passing themixture being analysed through a tube or a column so that the mixturepasses the regions with different recognising reagents successively, andin each such region a corresponding chosen component is grouped.

One of preferable variants of said forming of the probe volume and,respectively, working surface from several spatially separated regions,with providing for recording said signal for each of said regions,consists in that each of these regions is provided with a separatemagnetic induction meter, which is used to record said signal at acombinatorial frequency as described above. To do so, the output of eachinduction meter is connected with a radio-frequency filter, which istuned to pass the combinatorial frequency signal, and a receiver of theoutput signal. In doing so, the probe volume is formed, for example, bymaking use of arrays of a large number of cells (wells), in each cellthe grouping (selective binding) of a chosen component is ensured, andeach cell is equipped with an independent magnetic induction meter.Standard titer plates, which are used in conventional biochemicalanalysis procedures, are preferably to employ as such arrays. Apromising way is miniaturisation of such arrays. In particular, forrecognition of complex mixtures and multi-component analyses, forexample, relying on combinatorial chemistry methods, fabrication of thearrays of said regions as microelectronic chips is promising. In doingso, magnetic induction meters and circuitry components are preferable tomake on the basis of planar microelectronic technology.

In other variants of the method, in which the probe volume and,respectively, the working surface are formed from a number of spatiallyseparated regions and recording of said signal is enabled for each ofsaid regions, this signal is recorded successively for said regions. Indoing so, said probe volume consists of a number of spatially separatedregions and is built so as to enable successive testing of said regionswith a magnetic induction meter. For example, the probe volume isconstructed so that said regions can be successively placed near themagnetic induction meter, or the magnetic induction meter near saidregions. For example, a tube (column) is used, in which a probe volumeis formed consisting of a number of regions, spatially separated alongthis tube (column). Therewith, in these regions different recognisingreagents are immobilised which bind different chosen componentsselectively when the medium being analysed is passed through this column(tube). After this binding, the tube (column) is pulled in the immediatevicinity of the magnetic induction meter (e.g., pulled through aninductance coil), or the magnetic induction meter is moved along thetube (column). Beside such a tube, other formats can also be used. Theexamples are: a thick enough strip of a capillary-porous material, whichstrip is constructed and operates similarly to the tube, atwo-dimensional array of said regions scanned with a magnetic inductionmeter, etc.

In order to ensure that the recording of the signal for each of saidregions is independent of other regions, it makes sense to separatethese regions with broad enough intermediate space. For example, in theabove-described variant of the tube (column) inserted into the magneticinduction meter made as an inductance coil the distance between saidregions along the tube should be of the same and preferably more thantwice the diameter).

Furthermore, let us show that it is the distinctive features of theproposed method that provides the wanted technical result.

The grouping in a prove volume of a chosen component with magneticparticles attached to it provides for the enhancement of the method'ssensitivity. Simultaneously, this lowers the cost of the method,improves the efficiency of the measurement operations, simplifies theapparatus, and lowers its weight and dimensions.

The same technical result is ensured by making said magnetic fieldalternating, pro-setting its spectrum with spectral components, atleast, at two frequencies, and measuring said signal at a frequency,which is a linear combination of frequencies of said spectral componets,during the exposure of said magnetic particles to said protection of themethod against interference for a number of reasons. On of the reasonsis avoiding dc measurements, which are always associated with theproblem of drifts of a zero level, which is difficult to solve. Anotherreason is the absence of spectral components of acting signals in thespectrum of the signal extracted for the measurements, the orthogonalityof the signals in a broad sense, which is the conventional criterion ofhigh stability against interference. Short time duration of themeasurements also favours the efficiency of the proposed method. Of evengrater importance is the fact that recording of the signal during theexposure of the magnetic particles to the magnetic field enables one toavoid relying on the residual magnetisation of the particles, which isvery low in the most operable magnetic particles is substantiallyextended and the useful signal sharply increases. As this takes place,the technical result is realised, which consists in the enhancement ofthe signal-to-noise ratio resulting from the measurements, the increaseof the accuracy of the measurements, the enhancement of the sensitivityof the method, and mire reliability of the data obtained. At the sametime, the costs of the experiment are lowered owing to the reduction ofthe number of necessary operation steps, time, amount and dimensions ofnecessary equipment. This enables the development of mobile,inexpensive, highly efficient mass test laboratories, and improves theoperational flexibility of the method.

In preferable variants of the proposed method said linear combination ofthe frequencies of said spectral components is the sum of the differenceof these frequencies. This ultimately narrows the used frequencyspectrum, and, in turn, simplifies the embodiments of the method,reduces its costs, and improves the reliability.

Thus the proposed method allows achieving the wanted technical resultsin the simplest way and, hence, with minimal expenses.

It is also very important that the amplitude of, at least, one of saidspectral components is chosen high enough to ensure a non-lineardependence of said magnetic induction on the strength of said magneticfield. The reason is that it is the non-linearity of the energytransformation of acting signals in the magnetic particle material thatresults in the appearance of signal at a combinatorial frequency. Inthis case, the signal at the higher frequency should have preferably alesser amplitude, because this signal plays the role of interferencewhen the measured signal is distinguished on its background (in thetemporal sense). This interference could considerably lower thesensitivity of the proposed method. therefore the amplitudes A_(h) andA_(l) of said spectral components, which pertain to the higher and thelower frequencies, respectively, are chosen according to therelationship A_(l)/A_(h≦2.)

Besides, the magnetic strength vectors pertaining to, at least, two saidspectral components are oriented in a number of cases non-collinear toeach other. This is thought useful to raise the efficiency of the actionof the external signal energy on the system of magnetic labels, forexample, when recording spin echo signals. This provides the acdecoupling of the inductance coils and the absence of the influence ofthe magnetic field of one coil to the other one when the axis of onecoil is turned by 90° with respect to the other. Besides, this enablesone to optimise the conditions of nonlinear interaction of the actingsignals with the material of magnetic particles and hence to increasethe level of the extracted signal. This increases the sensitivity of themethod, which is the basis of all other above-mentioned characteristicsof the wanted technical result.

The magnetic particles are made of a soft magnetic material to enhancethe response of the particles to the acting magnetic field, because thisresponse determines the value of the measured signal. This also providesthe basis for the achievement of the wanted technical result.

The condition that in the probe volume a working surface isintentionally formed, and this surface meets the requirements for therecorded reaction of selective binding of a chosen component to occur,enhances the usable signal and, besides, increases the reliability ofthe results of the analysis. Further possibilities for the enhancementof the usable signal are opened through the use of a highly developedworking surface with a high effective surface value or athree-dimensional binding matrix, since the probability and the numberof elementary events of the mentioned binding increase with the increaseof the effective surface accessible to the reaction.

One of the methods of the working surface formation consists in fillingthe probe volume with micro-granules. This provides for the increase ofthe surface accessible for the reaction to occur and hence the signal tobe measured. In this case said granules are advisable to produce, forexample, under low pressure from polyethylene stabilised withgamma-radiation. This provides for high stability of the working surfaceagainst destructive factors of chemical and mechanical nature. It shouldbe noted that making use of polyethylene lowers the cost of the methodas well. Besides, the accuracy and the reliability of the results areincreased, since the chemical stability of polyethylene ensures theabsence of undesirable side effects from the material on which theworking surface is formed. Furthermore, one should take into account theability of polyethylene produced under low pressure and stabilised withgamma-radiation to form micro-granules of size less than one micron.This ensures the formation of a high effective surface and, besides,increases the accuracy of the analysis method, its sensitivity andefficiency. Besides, the possibility for reducing the size of saidspatially separated regions and, hence, of their denser arrangement isensured. Similarly, filling the probe volume with a capillary-porousstructure also enables one to increase the surface where biochemicalreactions occur and, hence, the signal being measured.

All this makes the proposed method stable against external effects, suchas mechanical (shaking, vibrating), thermal and chemical ones, since thepresence of a solid carrier of the reaction products being analysedimproves their isolation from the environment under the conditions of atransportable laboratory. The combined use of different formats of thereaction product carriers improves the reliability of the exploitationof the proposed method, ensures its operational flexibility, and extendsits application area.

The immobilisation of a reagent, which is capable of selectively bindingthe analyte, on the working surface enables one to efficientlydistinguish the information relevant just to the analyte from probableparasitic signals, increase the accuracy and the reliability of theresults of the analysis.

The formation of the probe volume from a number of spatially separatedregions with the possibility to record said signal for each of saidregions independently enables a multi-parameter analysis of the mixturesunder examination with a high degree of parallelisation. This allowslowering costs, when multi-parameter examinations are carried out, givesuniversality and operational flexibility to the proposed method,simplifies its apparatus embodiment, reduces dimensions and weight,opens opportunities for the development of mobile stations andlaboratories for mass tests of probes and investigations of population.

Besides, the formation of the probe volume from a number of spatiallyseparated regions with the possibility of their independent and parallelmonitoring substantially increases the throughput of the proposedmethod, lowers the cost per one analysis, improves the reliability ofthe results obtained, taking into account the increase in the amount ofstatistical data.

The condition that in said regions a working surface is formed withimmobilising on the surface various reagents, which are capable ofbinding various analytes selectively and through which chosen componentsare being bound to the working surface, and from recording said signalfor each of several said regions the information on the contents ofseveral analytes in the mixture being analysed is being obtained,provides for the same technical result applying to the analysis ofcomplex mixtures for the contents of a number of componentssimultaneously and to the recognition of such mixtures.

As a realisation of the method discussed above, an apparatus is proposedto read information in the method of analysis of a mixture of biologicaland/or chemical components. This apparatus refers to the field ofdevelopment and improvement of apparatus for registration of the resultsof biochemical analyses. The drawbacks of the analogue-apparatus areeliminated in the proposed apparatus for analysis of a mixture ofbiological and/or chemical components, which comprises:

-   -   a chosen component of the mixture being analysed, said component        being spatially arranged in a prescribed manner;    -   magnetic particles attached to the chosen component of the        mixture being analysed, directly or through an intermediate        material;    -   a magnetic field generator, within which action said magnetic        particles are situated;    -   a meter of the magnetic induction produced by said magnetic        particles;    -   an output signal receiver;    -   a block generating the result, which input is connected to the        output of the output signal receiver, which elements coincide        with essential features of the analogue-apparatus.

The difference from the prototype consists in that:

-   -   the chosen component of the mixture being analysed with magnetic        particles attached to this component is grouped in a probe        volume;    -   the magnetic field generator is made so as to allow presetting        the frequency spectrum of the magnetic field with spectral        components, at least, at two frequencies;    -   a radio-frequency filter is included, which input is connected        to the output of the magnetic induction meter, and the output of        the filter is connected to the output signal receiver, the        filter being tuned to pass the signal at a picked-out frequency,        which is a linear combination of the frequencies of said        spectral components.

Besides, said linear combination of the frequencies of said spectralcomponents is the sum or the difference of these frequencies.

Besides, the magnetic field generator comprises an alternating current(ac) generator made so as to allow presetting the frequency spectrum ofits output signal with spectral components, at least, at twofrequencies, and an inductive block connected to the output of said acgenerator, the output of the inductive block being the output of themagnetic field generator.

Besides, said inductive block serves as said magnetic induction meter.

Besides, said inductive block is made as an inductance coil with nocore, the first lead of the coil being connected to the output of saidac generator and the second lead being connected to chassis.

Besides, said inductive block comprises two inductance coils withoutcores, the first leads of said coils being connected, respectively, tothe first and the second output of said ac generator, the second leadsof the coils being connected to chassis, and, besides, the first lead ofone of said coils being connected to the input of said radio-frequencyfilter.

Besides, the axes of said coils are tilted with respect to each other.

Besides, the angle between the axes of said coils is 90°.

Besides, a phase regulator is inserted between one of the outputs ofsaid ac generator and the associated first lead of one of said coils,said phase regulator being provided with a control input for enteringthe data on the angle that the axis of this coil makes with the axis ofthe other coil.

Besides, the magnetic induction meter comprises an inductive elementwith no core, said element being not a part of said magnetic fieldgenerator.

Besides, the magnetic induction meter comprises a magnetoresistive(magneto-impedance) sensitive element.

Besides, the magnetic induction meter comprises a sensitive elementbased on the Hall effect.

Besides, the magnetic induction meter is made as a planarmicroelectronic structure.

Besides, the radio-frequency filter has the property to reject thesignal of that of the frequencies of said spectral components, which isthe nearest to said picked-out frequency.

Besides, the radio-frequency filter has the property to reject thesignal of that of the frequencies of said spectral components, which isthe nearest to said picked-out frequency, and, besides, theradio-frequency filter is controllable, the control input of theradio-frequency filter being connected to the control output of said acgenerator.

Besides, a reference signal generator is inserted, which is connectedthrough its input to the output of said ac generator, through thesecond, control, input to the output of the output signal receiver, andthrough its output to the second input of said radio-frequency filter,said filter being made lock-in.

Besides, a control block is inserted, which first and second outputs areconnected to the control inputs of said ac generator and saidradio-frequency filter, respectively, and the input is connected to thecontrol output of the output signal receiver.

Besides, the reference signal generator and the output signal receiverare made as a processor.

Besides, the output signal generator, the output signal receiver, andsaid ac generator are made as a processor.

Besides, the magnetic particles are made of a soft magnetic material.

Besides, in said probe volume a working surface is formed, to which thechosen component of the mixture being analysed is bound, said magneticparticles being attached to this component.

Besides, the working surface is formed in the probe volume filled withmicro-granules.

Besides, said micro-granules are made of polyethylene.

Besides, said micro-granules are produced under low pressure frompolyethylene stabilised with gamma-radiation.

Besides, the working surface is formed in the probe volume filled with acapillary-porous structure.

Besides, on the working surface a reagent is immobilised, which iscapable of selectively binding the analyte, the chosen component of themixture being analysed being bound to said reagent, and, through thisreagent, to the working surface.

Besides, said probe volume consists of several spatially separatedregions, each of these regions being provided with a separate magneticinduction meter, which output is connected to a radio-frequency filterand an output signal receiver.

Besides, said probe volume consists of several spatially separatedregions and is made so as to enable successive testing of said regionswith a magnetic induction meter.

Besides, the ac generator and the output signal receiver are made as aprocessor.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1. is a block diagram of an apparatus in accordance with theinvention.

FIG. 2. is a block diagram of another apparatus in accordance with theinvention.

FIG. 3. is a block diagram of another apparatus in accordance with theinvention.

FIG. 4. is a block diagram of another apparatus in accordance with theinvention.

FIG. 5. is a block diagram of another apparatus in accordance with theinvention.

FIG. 6. is a block diagram of another apparatus in accordance with theinvention.

FIG. 7. is a block diagram of another apparatus in accordance with theinvention.

FIG. 8. is a block diagram of another apparatus in accordance with theinvention.

FIG. 9. is a block diagram of another apparatus in accordance with theinvention.

FIG. 10. is a block diagram of another apparatus in accordance with theinvention.

FIG. 11. is a block diagram of another apparatus in accordance with theinvention.

FIG. 12. is a block diagram of another apparatus in accordance with theinvention.

FIG. 13. is a block diagram of another apparatus in accordance with theinvention.

In FIG. 1 the basic variant of a proposed apparatus according to theinvention is schematically shown.

In FIG. 2 the variant of a proposed apparatus according to the inventionis schematically shown, with the magnetic field generator made from anac generator and an inductive block connected in series.

In FIG. 3 the variant of a proposed apparatus according to the inventionis schematically shown, with the inductive block functioning as themagnetic induction meter.

In FIG. 4 the variant of a proposed apparatus according to the inventionis schematically shown, with the inductive block made as an inductancecoil.

In FIG. 5 the variant of a proposed apparatus according to the inventionis schematically shown, with the inductive block made as two inductancecoils.

In FIG. 6 the variant of a proposed apparatus according to the inventionis schematically shown, with the inductive block made as two inductancecoils tilted at a certain angle with respect to each other.

In FIG. 7 the variant of a proposed apparatus according to the inventionis schematically shown, with the inductive block made as two inductancecoils tilted at a certain angle with respect to each other, and with aphase regulator in the circuit of one of the coils.

In FIG. 8 the variant of a proposed apparatus according to the inventionis schematically shown, with the inductive block made as an inductancecoil and with a rejecting filter in the signal receiving circuit.

In FIG. 9 the variant of a proposed apparatus-according to the inventionis schematically shown, where the filter is lock-in.

In FIG. 10 the variant of a proposed apparatus according to theinvention is schematically shown, where connections of a control blockare depicted provided that this block is included in the apparatus.

In FIG. 11 the variant of a proposed apparatus according to theinvention is schematically shown, with a processor combining thefunctions of a reference signal generator and output signal receiver.

In FIG. 12 the variant of a proposed apparatus according to theinvention is schematically shown, with a processor combining thefunctions of the ac generator, the output signal receiver, and thereference signal generator.

In FIG. 13 the variant of a proposed apparatus according to theinvention is schematically shown, with a processor combining thefunctions of the ac generator and the output signal receiver. p In FIGS.1 to 13 the following notations are used:

1, magnetic field generator; 2, the total of magnetic particles attachedto chosen component of the mixture being analysed and grouped in a probevolume; 3, magnetic induction meter; 4, radio-frequency filter; 5;output signal receiver; 6, block generating the result; 7; ac generator;8, inductive block; 9, first inductance coil; 10, second inductancecoil; 11, phase regulator; 12, reference signal generator, 13, controlblock; 14, processor.

Modes of Carrying Out the Invention

The proposed method can be realised by apparatus for analysis of amixture of biological and/or chemical components.

The proposed apparatus operates as follows. The generator 1 acts with analternating magnetic field on the magnetic particles 2 (FIG. 1). Forexample (FIG. 4) the generator 1 produces the alternating magnetic fieldinside the coil 9. The magnetic field has, at least, two spectral(frequency) componets, for example, with the frequencies f₁=100 kHz andf₂=100 Hz. The response of the magnetic particles to their exposure tothe magnetic field is their magnetisation or magnetic induction. Oneexploits the particles, which possess magnetic properties to one extentof another, in particular, non-linear dependences of the magnetisationand the magnetic induction on the strength of an external magneticfield. Owing to this a spectral re-distribution of the excitation energyoccurs. and combinatorial spectral components arise in the spectrum ofthe magnetic particles response to the action of the field. In general,these components are linear combinations of frequencies f₁ and f₂ of theform f_(i)=mf₁+nf₂, where m,n are positive or where m, n are positive ornegative integers other than zero. In principle, such a linearcombination may also be contributed of by more spectral components. Thevalues of m and n can vary, as the case requires. For example, saidlinear combination may have the form f₁=f_(l)±f₂ (the sum and thedifference frequencies), f_(i)=f_(l)±2 f₂, and so on. It is known thatthe intensity of spectral components decrease with the harmonic number.Therefore, to obtain the maximum signal amplitude, the values m=l andn=±l are preferable to use. This corresponds to the sum or thedifference of the frequencies of spectral components of the actingmagnetic field.

Let us remind that prior to the measurements the chosen component andthe magnetic particles attached to it are spatially arranged in aprescribed manner and grouped in the probe volume, for example, throughthe reaction of selective binding of the chosen component by acomplementary recognising reagent. The chosen component is considered tobe either the analyte itself or another component (e.g., which competeswith the analyte for binding to the recognising reagent), intrinsic tothe mixture being analysed or intentionally introduced into thismixture, the quantitative measure of the grouping of said chosencomponent in the probe volume indicating the content of the analyte inthe mixture being analysed.

The magnitude of the recorded magnetic induction signal at acombinatorial frequency is unambiguously determined by the amount of themagnetic particles 2 grouped in the probe volume. Consequently, onextracting the signal at a combinatorial frequency with the filter 4, onobtains the information of the amount of the magnetic labels 2 in theprobe volume from the output of the receiver 5. To do this, the receiver5 is made in accordance with any known scheme, which are used in themethods of noise-immune receiving of low-intensity signals against anoise and interference background. the receiver 5 fulfils also thefunctions of amplification, detection, and accumulation.

The eventual result, i.e., quantitative data on the content of theanalyte, is formed by the block 6 for generating the result. Theparameters of the block 6 take into account specific features of thesample of the mixture being analysed and the operations performed withit.

In a preferable variant of the apparatus the magnetic field generator 1consists in an ac generator 7, which is made so as to allow pre-settingthe frequency spectrum of its output signal with spectral components, atleast, at two frequencies, and an inductive block 8 connected to theoutput of said ac generator 7 (FIG. 2). This enables the required actionon the sample being tested. As discussed earlier for the proposedmethod, the pre-setting of the frequency spectrum is advisable to takeinto account spectral features of the interaction of the generatedhigh-frequency magnetic field with the sample being measured.

As this takes place, one can significantly simplify the apparatus, ifsaid inductive block 8 of the magnetic field generator servessimultaneously as the magnetic induction meter 3 (FIG. 3). This isreasonable in magnetic measurements, in which a common coil oftenoperates simultaneously as an exciting coil and as a receiving one. Thisvariant is preferable for one-channel apparatus. However, thesefunctions are advisable to separate for multi-channel apparatus, inwhich the probe volume consists of a number of spatially separatedregions. For example, the block 8 generates a magnetic field common forall said regions, and each region is provided with an individualmagnetic induction meter. Another case of separating these functions ismaking the meter 3 on the basis of not inductive, but anothermagneto-sensitive element (see below).

In the simplest variant, said inductive block 8, which also serves asthe magnetic induction meter, is made as an inductance coil 9 with nocore, the first lead of this coil being connected to the output of saidac generator 7, and the second lead being connected to chassis (FIG. 4).

In another variant of the proposed apparatus (FIG. 5), in the inductiveblock a second inductance coil 10 is included, which is connectedthrough its first lead to the second output of the generator 1, andthrough the second lead to chassis. In this case one of the spectralcomponents of the output signal comes from the first output of thegenerator 1 to the coil 9, and the other spectral component does fromthe second output of the generator 1 to the coil 10.

In another variant of the proposed apparatus (FIG. 6), the axes of saidcoils 9 and 10 are tilted with respect to each other. As a result, themagnetic field strength vectors of two said spectral components makesome angle in the sample 2. Due to variation of this angle in the sampleunder test it is possible to raise the efficiency of the non-lineartransformation of partial components of the magnetic field into themagnetic induction signal to be recorded, and hence to increasesignal-to-noise ratio.

As this takes place, the angle between the axes of said coils is 90° inone of realised variants of the apparatus.

In another variant of the proposed apparatus (FIG. 7), a phase regulator11 is included, which is inserted between one of the outputs of saidgenerator 1 and the associated inductance coil 9 or 10, said phaseregulator being equipped with a control input for entering the data φ₀on the angle that the axis of this coil makes with the axis of the othercoil. This opens additional opportunities to control the phase of one ofspectral components of the exciting signal.

If, for some reasons, it is advisable to separate the magnetic inductionmeter 3 and the magnetic field generator 1, one may realise the meter 3using a number of alternative methods of magnetic inductionmeasurements. For example, in the scheme of FIG. 1 the magneticinduction meter comprises an inductive element with no core, or amagnetoresistive (magneto-impedance) sensitive element, or a sensitiveelement based on the Hall effect. As this takes place, in a preferablevariant of the apparatus the magnetic induction meter is made as aplanar microelectronic structure.

In another variant of the proposed apparatus, which can be illustratedby any of the schemes of FIGS. 1 to 7 and others, except for thevariants in which the filter 4 is lock-in, the filter 4 is a rejectingfilter, which has the property to suppress that spectral component ofthe acting signal, which is the nearest to said picked-out frequency.Then, if the Q-factor of said filter 4 is high enough, even powerfulinterference at the frequency neighbour to the picked-out one can besuppressed down to a sufficiently low level without noticeableattenuation of the usable signal.

It should be noted that the higher of the two frequencies of the actingsignal spectrum is usually rejected. The combinatorial frequency lies,of course, near the higher frequency, which signal, if no rejection,could come to the receiver 5 and substantially degrade signal-to-noiseratio.

In another variant of the proposed apparatus (the scheme of FIG. 8), thefilter 4 is made controllable, and its control input is connected to thecontrol output of the generator 7, the frequency of which signal is thenearest to said picked-out frequency. The introduced connection of thementioned output of the generator 7 to the control input of the filter 4enables one to tune the frequency rejected by the filter 4, thuscompensating for instabilities of said generator 7.

In this case one should note that the characteristics of interferencesuppression by filters usually correlate with the absolute value of thefrequency shift of a picked-out frequency relative to the transmissionband of the filter 4. It is known that the frequency drift of agenerator signal is usually proportional to its nominal frequency.Therefore, in the proposed apparatus one expects the drift of thehigh-frequency spectral component of the generator 7 to be 3 ordershigher than that of the low-frequency component. That is why the filter4 is tuned by the signal of the higher frequency of the acting signalspectrum. It is this frequency that is the closest to the picked-outcombinatorial frequency.

In the proposed apparatus (the scheme of FIG. 9), the reference signalgenerator 12 receives at its input the exciting signal from the outputof the generator 1, which has, for example, two spectral components.Then, the reference signal generator 12 yields at its output a harmonicsignal at a combinatorial frequency, this signal being used as areference (locking) signal for the lock-in filter 4. The latter is amultiplier. It picks out the corresponding combinatorial component fromthe mixed signal and noise in the optimal manner, according to theKotel'nikov's theory. Account is taken of further accumulating of themultiplication result in the output signal receiver 5, and making themultiplied components in phase through tuning the reference signalgenerator 12, which control input receives the feedback signal from theoutput of the output signal receiver 5.

In another variant of the proposed apparatus (FIG. 10), a control block13 is inserted, which first and second outputs are connected to thecontrol inputs of said generator 7 and said radio-frequency filter 4,respectively, and the input is connected to the control output of theoutput signal receiver 5. By analysing a change in the output signal dueto changes in the parameters of the generator 7 and the filter 4, thecontrol block 13 generates the optimal controlling action on said blocks7 and 4 through feedback loops.

In another variant of the proposed apparatus (FIG. 11), a processor 14combines the functions of said reference signal generator 12 and saidreceiver 5. This is advisable from the viewpoint of using moderntechnology capabilities, and for the compatibility of the proposedapparatus with modern component types.

In another variant of the proposed apparatus (FIG. 12), a processor 14combines the functions of said reference signal generator 12, receiver5, and ac generator 7. This is advisable for the same reasons.

In another variant of the proposed apparatus (FIG. 13), a processor 14combines the functions of said ac generator 7 and output signal receiver5. This is advisable for the same reasons.

It should be pointed out that in addition to the above-mentionedvariants of combinations of block functions in one processor variouscombinations of these variants are possible as well, including those inwhich the processor fulfils simultaneously the functions of the controlblock 13.

Furthermore, let us show that it is distinctive features of the proposedapparatus that ensures the wanted technical result.

The grouping of a chosen component of the mixture being analysed, withmagnetic particles attached to it, in a probe volume provides for theincrease in the apparatus sensitivity and the improvement of parametersof its output signal. This is due to the increase of the number ofparticles, magnetic induction carriers, in the confined probe volume,where the measurements are carried out, in close proximity to themagnetic induction meter. The latter can be miniature and, in a numberof cases, realised on the basis of the planar microelectronicstechnology. All these features allow lowering the cost of the apparatus,simplifying its embodiment, and decreasing weight and dimensions aswell. Besides, the efficiency of the measurements is improved, since therealisation of the characteristics needed without pre-concentratingmagnetic particles would require the use of data accumulation methodsassociated with extra time and device needs.

The realisation of the magnetic field generator with the capability ofpre-setting the frequency spectrum of the magnetic field with spectralcomponents, at least, at two frequencies, and the insertion of aradio-frequency filter between the output of the magnetic inductionmeter and the input of the output signal receiver, said filter beingtuned to pass the signal of the picked-out frequency, which is a linearcombination of the frequencies of said spectral components, enables oneto drastically enhance the usable signal against noise and to improvethe stability and the immunity to interference for a number of reasons.Among these reasons, first, is going away from relying on the residualmagnetisation of particles, which is very low for small particles.Second, it is avoiding dc measurements, which are always associated withthe problem of zero drifts, which is difficult to solve. Third, theseare the absence of spectral components of acting signals in the spectrumof the signal picked-out for measurements and the orthogonality of thesesignals in broad sense. The latter condition is the conventionalcriterion of high immunity to interference and enables one toefficiently distinguish the information signal from the externalmagnetic field, fluctuation noise, and apparatus interference.

In doing so, the technical result is achieved, which consists in theincrease of the signal-to-noise ratio resulted from the measurements,increase in the measurement accuracy, enhancement of the apparatussensitivity, improvement of the reliability of the data obtained, withsimultaneous lowering of experimental costs owing to the reduction ofthe number of operations needed, time, amount and dimensions ofapparatus needed, in the opportunities for the development of mobile,inexpensive, high-throughput mass test laboratories, and, hence, inhigher operational flexibility of the proposed apparatus.

The feature that the picked-out frequency is the sum or the differenceof the frequencies of said spectral components of the acting magneticfield narrows the used frequency band ultimately, provides formaximising the amplitude of the generated usable signal owing tominimising the number of a picked-out harmonics. This also improvesstability and immunity to interference, simplifies the deviceembodiment, lowers cost, and improves reliability. Thus, the proposedapparatus provides for achieving the above-mentioned wanted technicalresults in the simplest way and with minimal expenses.

One should note that, in general, an alternating magnetic fieldgenerator could be realised in different ways, for example, with arotating magnet or with an ac generator. In the latter case, as shown inFIG. 2, the magnetic field generator comprises an ac generator made soas to allow presetting the frequency spectrum of the output signal withspectral components, at least, at two frequencies, and an inductiveblock connected to the output of said ac generator. This technicalsolution provides for the reduction of the apparatus dimensions due tothe use of modern microelectronic technologies. In doing so, thefunctions of a number of electronic blocks are eventually combined in aprocessor (block 14 in FIGS. 11 to 13), ensuring the above-mentionedwanted technical result.

Besides, the feature that said inductive block of the magnetic fieldgenerator fulfils the functions of the magnetic induction meter, ensuresthe compactness of the realised technical solution, improves thereliability of the apparatus, lowers its cost, thus providing the basisfor the realisation of the above-mentioned technical result.

This is also favoured by making said inductive block as an inductancecoil with no core, the first lead of the coil being connected with theoutput of said ac generator, and the second lead being connected tochassis. Actually, the absence of the core lowers internal noise of theapparatus, eliminates the noise intrinsic to a core, which is due to theinhomogeneity of magnetisation processes in magnetic materials, andlowers the weight and the dimensions of the apparatus. This also opensthe possibilities for the miniaturisation of the apparatus and theemployment of modern microelectronic technologies. The mentioned factorsprovide for further lowering of the measurement threshold, enhancingsensitivity, and improving stability and immunity to interference of theapparatus.

The feature that said inductive block comprises two inductance coilswith no cores, first leads of said coils being connected to,respectively, the first and the second outputs of said ac generator,second leads being connected to chassis, and, besides, the first lead ofone of the coils being connected to the input of said filter, enablesone to realise the filter 4 of higher orders and higher Q-factors,taking into account parasitic capacitances and inductances usuallyexisting in schemes. Consequently, the apparatus possesses higherstability against interference and hence the above-mentioned wantedtechnical result is ensured.

The feature that the axes of said coils are tilted with respect to eachother results in that the magnetic fields of the two spectral componentsare crossed at some angle in the sample. In this case, variation of thecrossing angle in the sample under test provides for extra possibilitiesto gain the efficiency of non-linear interaction of the spectralcomponents of the exciting signal with magnetic particles 2 of thesample under test. This favours for further lowering of the measurementthreshold, increase of sensitivity, immunity and stability tointerference of the apparatus.

The feature that the rotation angle of the axis of the second coilrelative to the first one is 90° ensures the conditions needed to theuse of alternative methods for information signal formation, e.g., usingspin precession.

This is also favoured by that the phase regulator 11 is inserted betweenthe second output of the alternating current generator 7 and the firstlead of the second inductance coil, the data φ₀ on the rotation of thesecond coil axis relative to the first one entering the control input ofthe phase regulator. The mentioned features also lead to the wantedtechnical result.

The presence of the inductance coil with no core in the magneticinduction meter 3 has the same advantages as the presence of a similarcoil in the inductive block 8. This solution is preferable for theapparatus discussed, which measures very small quantities, because ofboth the high apparatus sensitivity needed and a low signal amplitude atthe picked-out frequency, which results from a combinatorial interactionunder the condition of magnetic non-linearity of the material ofmagnetic particles.

Besides, to tackle the problems in broad ranges of external parametersand to ensure the functional flexibility of the apparatus, the magneticinduction meter contains either a magnetoresistive (magneto-impedance)sensitive element or a sensitive element based on the Hall effect.Furthermore, it is advisable to make said magnetic induction meter as aplanar microelectronic structure. Then it could be realised on the basisof industrial microelectronic technologies and mass production, thusproviding for lowering of costs, weight, and dimensions of theapparatus, and improvement of its reliability.

The wanted technical result is favoured also by that the radio-frequencyfilter has the property to reject that harmonic component of theexciting signal, which has the frequency nearest to the picked-outcombinatorial frequency. The reason is that the most dangerousinterference is eliminated, which otherwise could influence thesensitive cascades of the receiver by bringing non-linear componentsinto the received signal spectrum, lower signal-to-noise ratio andreliability of the results obtained.

Further improvement of the quality of the information receiving withsimultaneous reduction in the requirements to the device quality isensured by that the radio-frequency filter 4 is made controllable, itscontrol input being connected to the control output of the generator 7.In this case the requirements for the stability of the generator 1 canbe substantially reduced, since the drift of the exciting signalfrequency is compensated for by proper tuning of the filter 4characteristics.

The feature that the reference signal generator 12 is introduced, whichhas the input connected to the output of said ac generator 7, thesecond, control, input, connected to the output of the output signalreceiver 5, and the output connected to the second input of saidradio-frequency filter 4, which is made lock-in, ensures further gain inthe efficiency of distinguishing weak information signals from noises.This enables one to realise optimal conditions for signal receiving andto achieve the wanted technical result.

Further opportunities to improve the apparatus arise from that thecontrol block 13 is introduced, which first and second outputs areconnected with control inputs of said ac generator 7 and radio-frequencyfilter 4, respectively, and the input of the block 13 is connected tothe control output of the output signal receiver 5. In this case thecontrol block 13, which functions can be fulfilled by a microprocessoror a computer, analyses the change of the output signal with changes ofparameters of the generator 7 and the filter 4, and, as a result,generates the optimal controlling action on said blocks 7 and 4 throughfeedback loops. In doing so, ultimate characteristics of the apparatusare realised, the operational flexibility is improved and theapplication area is extended.

Further opportunities to improve the apparatus stem from that thefulfilment of the functions of various combinations of blocks in theproposed apparatus, except for the inductive block 8, block 6 formingthe result, and the filter 4, is ensured through the introduction of theprocessor 14, e.g., made as a microprocessor or a computer. In doing so,ultimate characteristics of the apparatus are realised, operationalflexibility is improved, and the application area is extended. Besides,this opens the possibility to develop mobile, inexpensive,high-throughput laboratories for mass tests.

Thus, it is shown that the wanted technical result is actually achievedowing to the distinctive features of the proposed apparatus. Theexperiments done have demonstrated the feasibility of the proposedmethod and apparatus.

INDUSTRIAL APPLICABILITY

The proposed method and apparatus can be used for biological andchemical analyses, and also for development of chemical and biologicalsensors.

1. A method of analysis of an analyte in a mixture of biological and/orchemical components, comprising: a) contacting magnetic particles withthe analyte to attach the magnetic particles thereto or using theanalyte that is already attached to magnetic particles, the magneticparticles possessing the property of a non-linear dependence of themagnetization and magnetic induction on the strength of an externalmagnetic field, b) exposing the magnetic particles attached to theanalyte to a magnetic field, c) recording a signal due to the magneticinduction produced by the magnetic particles as a result of theirexposure to the magnetic field, d) generating quantitative data on thecontent of the analyte in the mixture being analysed from the value ofthe signal, wherein e) the magnetic field has a spectrum, and thespectrum is pre-set with spectral components at least at twofrequencies, wherein the amplitude of at least one of the spectralcomponents is chosen high enough to ensure a non-linear dependence ofthe magnetic induction on the strength of the magnetic field, and thesignal is recorded at such a frequency that is a linear combination ofthe frequencies of the spectral components during the exposure of themagnetic particles to the magnetic field.
 2. The method as defined inclaim 1, wherein the amplitudes of the spectral components are A_(h) andA₁, which pertain to the higher and the lower frequencies, respectively,and are chosen according to the relationship A_(l)/A_(h)>2.
 3. Themethod as defined in claim 1, wherein prior to step a): grouping theanalyte in a probe volume, the probe volume being at least one presetspatial region.
 4. The method as defined in claim 3, wherein groupingthe analyte in the probe volume is performed by one of the followingprocesses: by sedimentation, by exposure to an inhomogeneous magneticfield or by filtration.
 5. The method according to claim 3, wherein inthe probe volume a working surface is formed, and the analyte isspatially arranged through binding the analyte to the working surface.6. The method according to claim 5, wherein the working surfacecomprises micro-granules.
 7. The method according to claim 5, whereinthe working surface comprises a reagent capable of binding the analytein a selective manner.
 8. The method according to claim 3, wherein theprobe volume comprises several spatially separated regions, and thepossibility to record the signal is ensured for each of the regions. 9.The method according to claim 3, wherein the probe volume comprises aplurality of spatially separated regions, each region comprising anindependent working surface, each working surface comprising a reagentcapable of competitively binding a specific analyte, and by recordingthe signal for each of the regions the information on the contents ofdifferent analytes in the mixture is obtained.
 10. The method as definedin claim 3, wherein the probe volume comprises a working surface and theworking surface comprises micro-granules.
 11. The method as defined inclaim 10, wherein the micro-granules comprise polyethylene.
 12. Themethod as defined in claim 10, wherein the micro-granules are made underlow pressure from polyethylene stabilised with gamma-radiation.
 13. Themethod as defined in claim 10, wherein the probe volume comprises aworking surface and the working surface is a capillary-porous structure.14. The method as defined in claim 1, wherein the linear combination offrequencies of the spectral components is defined by the followingrelation:f _(i) =nf ₁ +mf ₂ where: f₁and f₂are the frequencies of the spectralcomponents of the magnetic field, n and m are positive or negativeintegers other than zero.
 15. The method as defined in claim 14, whereinm equals one and n equals plus or minus two.
 16. The method as definedin claim 1, wherein the magnetic particles are superparamagnetic. 17.The method according to claim 1 wherein the linear combination of thefrequencies of the spectral components is the sum or the difference ofthese frequencies.
 18. The method according to claim 1 wherein themagnetic particles are made of a soft magnetic material.
 19. The methodas defined in claim 1, wherein in step a), the magnetic particles areattached to the analyte through an intermediate material.
 20. A methodof analysis of an analyte in a mixture of biological and/or chemicalcomponents, comprising: choosing a component for attaching magneticparticles thereto or a component that is already attached to magneticparticles, wherein such component defines a chosen component, the chosencomponent allows generating quantitative data on the content of theanalyte in the mixture being analysed, introducing the analyte and thechosen component within a probe volume comprising a recognizing reagentcapable of binding the analyte and the chosen component in a competitivemanner, contacting magnetic particles with the chosen component, eitherbefore or after the step of introducing the analyte and the chosencomponent within the probe volume, to attach the magnetic particles tothe chosen component or using the chosen component that is alreadyattached to magnetic particles, exposing the magnetic particles attachedto the chosen component bound to the recognizing agent to a magneticfield, recording a signal due to the magnetic induction produced by themagnetic particles as a result of their exposure to the magnetic field,generating quantitative data on the content of the analyte in themixture being analysed from the value of the signal, the magnetic fieldhas a spectrum, and the spectrum is pre-set with spectral components atleast at two frequencies, wherein the amplitude of at least one of thespectral components is chosen high enough to ensure a non-lineardependence of the magnetic induction on the strength of the magneticfield; the signal is recorded at such a frequency that is a linearcombination of the frequencies of the spectral components during theexposure of the magnetic particles to the magnetic field, and whereinmagnetic field strength vectors pertaining to the at least two spectralcomponents are oriented non-collinear to each other.
 21. The method asdefined in claim 20, wherein the probe volume comprises micro-granules.22. The method as defined in claim 21, wherein the micro-granules aremade under low pressure from polyethylene stabilised withgamma-radiation.
 23. The method as defined in claim 21, wherein themicro-granules comprise polyethylene.
 24. The method as defined in claim20, wherein the probe volume comprises a capillary-porous structure. 25.The method as defined in claim 20, wherein the amplitudes of thespectral components are A_(h) and A₁, which pertain to the higher andthe lower frequencies, respectively, and are chosen according to therelationship A₁/A_(h)>2.
 26. The method as defined in claim 20, whereinthe magnetic particles are superparamagnetic.
 27. The method accordingto claim 20, wherein the probe volume comprises a working surfacespatially arranged within the probe volume, and the chosen component isspatially arranged through being bound to the working surface.
 28. Themethod according to claim 20, wherein the probe volume comprises aworking surface, the working surface comprising a plurality of spatiallyseparated regions, and the signal is respectively recorded for each ofthe regions.
 29. The method according to claim 20, wherein the probevolume comprises a plurality of spatially separated regions, each regioncomprising an independent working surface, each working surfacecomprising an independent recognizing reagent capable of binding arespective analyte and a respective chosen component in a competitivemanner and through which the respective chosen component is bound to theworking surface of the respective region, and by recording the signalfor each region the information on the contents of different analytes inthe mixture is obtained.
 30. The method as defined in claim 20, whereinthe magnetic particles are attached to the chosen component beforebinding to the recognizing reagent.
 31. The method as defined in claim20, wherein the chosen component is used in a known amount.
 32. Themethod as defined in claim 20, wherein the linear combination offrequencies of the spectral components is defined by the followingrelation:f _(i) =nf ₁ +mf ₂ where: f₁and f₂are the frequencies of the spectralcomponents of the magnetic field, n and m are positive or negativeintegers other than zero.
 33. The method as defined in claim 32, whereinm equals one and n equals plus or minus two.
 34. The method as definedin claim 20, wherein the magnetic particles are made of a soft magneticmaterial.
 35. The method according to claim 20, wherein the linearcombination of the frequencies of the spectral components is the sum orthe difference of these frequencies.
 36. A method of analysis of ananalyte in a mixture of biological and/or chemical components,comprising: choosing a component for attaching magnetic particlesthereto or a component that is already attached to magnetic particles,wherein such component defines a chosen component, the chosen componentallows generating quantitative data on the content of the analyte in themixture being analysed, introducing the analyte and the chosen componentwithin a probe volume comprising a recognizing reagent capable ofbinding the analyte and the chosen component in a competitive manner,contacting magnetic particles with the chosen component, either beforeor after the step of introducing the analyte and the chosen componentwithin the probe volume, to attach the magnetic particles to the chosencomponent or using the chosen component that is already attached tomagnetic particles, the magnetic particles possessing the property of anon-linear dependence of the magnetisation and magnetic induction on astrength of an external magnetic field, exposing the magnetic particlesattached to the chosen component bound to the recognizing reagent to amagnetic field, recording a signal due to the magnetic inductionproduced by the magnetic particles as a result of their exposure to themagnetic field, generating quantitative data on the content of theanalyte in the mixture being analysed from the value of the signal,wherein the magnetic field has a spectrum, and the spectrum is pre-setwith spectral components at least at two frequencies, wherein theamplitude of at least one of the spectral components is chosen highenough to ensure a non-linear dependence of the magnetic induction onthe strength of the magnetic field, and the signal is recorded at such afrequency that is a linear combination of the frequencies of thespectral components during the exposure of the magnetic particles to themagnetic field.
 37. The method as defined in claim 36, wherein theamplitudes of the spectral components are A_(h) and A₁, which pertain tothe higher and the lower frequencies, respectively, and are chosenaccording to the relationship A₁/A_(h)>2.
 38. The method as defined inclaim 36, wherein the probe volume comprises micro-granules.
 39. Themethod as defined in claim 38, wherein the micro-granules are made underlow pressure from polyethylene stabilised with gamma-radiation.
 40. Themethod as defined in claim 38 , wherein the micro-granules comprisepolyethylene.
 41. The method as defined in claim 36, wherein the probevolume comprises a capillary-porous structure.
 42. The method as definedin claim 36, wherein the magnetic particles are superparamagnetic. 43.The method according to claim 36, wherein the probe volume comprises aworking surface spatially arranged within the probe volume, and thechosen component is spatially arranged through being bound to theworking surface.
 44. The method according to claim 36, wherein the probevolume comprises a working surface, the working surface comprising aplurality of spatially separated regions, and the signal is respectivelyrecorded for each of the regions.
 45. The method according to claim 36,wherein the probe volume comprises a plurality of spatially separatedregions, each region comprising an independent working surface, eachworking surface comprising an independent recognizing reagent capable ofbinding a respective analyte and a respective chosen component in acompetitive manner and through which the respective chosen component isbound to the working surface of the respective region, and by recordingthe signal for each region the information on the contents of differentanalytes in the mixture is obtained.
 46. The method as defined in claim36, wherein the magnetic particles are attached to the chosen componentbefore binding to the recognizing reagent.
 47. The method as defined inclaim 36, wherein the chosen component is used in a known amount. 48.The method as defined in claim 36, wherein the linear combination offrequencies of the spectral components is defined by the followingrelation:f _(i) =nf ₁ +mf ₂ where: f₁and f₂are the frequencies of the spectralcomponents of the magnetic field, n and m are positive or negativeintegers other than zero.
 49. The method as defined in claim 48, whereinm equals one and n equals plus or minus two.
 50. The method as definedin claim 36, wherein the magnetic particles are made of a soft magneticmaterial.
 51. The method according to claim 36, wherein the linearcombination of the frequencies of the spectral components is the sum orthe difference of these frequencies.
 52. A method of analysis of ananalyte in a mixture of biological and/or chemical components,comprising: a) contacting magnetic particles with the analyte to attachthe magnetic particles to the analyte, or contacting the analyte withanother component that is attached to magnetic particles to attach theother component to the analyte, such component being selectivelybindable to the analyte, or contacting the analyte with anothercomponent that is attached to magnetic particles and bindable with theanalyte, and thereafter contacting the analyte attached to the anothercomponent with a recognizing reagent that is bindable with the analyteto attach the recognizing agent to the analyte attached to the anothercomponent, the magnetic particles possessing the property of anon-linear dependence of the magnetization and magnetic induction on thestrength of an external magnetic field, b) exposing the magneticparticles which are attached either directly or indirectly to theanalyte to a magnetic field, c) recording a signal due to the magneticinduction produced by the magnetic particles as a result of theirexposure to the magnetic field, d) generating quantitative data on thecontent of the analyte in the mixture being analysed from the value ofthe signal, wherein e) the magnetic field has a spectrum, and thespectrum is pre-set with spectral components at least at twofrequencies, wherein the amplitude of at least one of the spectralcomponents is chosen high enough to ensure a non-linear dependence ofthe magnetic induction on the strength of the magnetic field, and thesignal is recorded at such a frequency that is a linear combination ofthe frequencies of the spectral components during the exposure of themagnetic particles to the magnetic field.
 53. The method as defined inclaim 52, wherein the amplitudes of the spectral components are A_(h),and A₁, which pertain to the higher and the lower frequencies,respectively, and are chosen according to the relationshipA_(l)/A_(h)>2.
 54. A method of analysis of an analyte in a mixture ofbiological and/or chemical components, comprising: choosing a componentfor attaching magnetic particles thereto or a component that is alreadyattached to magnetic particles, wherein such component defines a chosencomponent, the chosen component allows generating quantitative data onthe content of the analyte in the mixture being analysed, contacting theanalyte and the chosen component with a working surface comprising arecognizing reagent capable of binding the analyte and the chosencomponent in a competitive manner, contacting magnetic particles withthe chosen component, either before or after the step of contacting theanalyte and the chosen component with the working surface, to attach themagnetic particles to the chosen component or using the chosen componentthat is already attached to magnetic particles, the magnetic particlespossessing the property of a non-linear dependence of the magnetizationand magnetic induction on the strength of an external magnetic field,exposing the magnetic particles attached to the chosen component boundto the recognizing agent to a magnetic field, recording a signal due tothe magnetic induction produced by the magnetic particles as a result oftheir exposure to the magnetic field, generating quantitative data onthe content of the analyte in the mixture being analysed from the valueof the signal, wherein the magnetic field has a spectrum, and thespectrum is pre-set with spectral components at least at twofrequencies, wherein the amplitude of at least one of the spectralcomponents is chosen high enough to ensure a non-linear dependence ofthe magnetic induction on the strength of the magnetic field, and thesignal is recorded at such a frequency that is a linear combination ofthe frequencies of the spectral components during the exposure of themagnetic particles to the magnetic field.
 55. The method as defined inclaim 54, wherein magnetic field strength vectors pertaining to the atleast two spectral components are oriented non-collinear to each other.56. A method of analysis of an analyte in a mixture of biological and/orchemical components, comprising: grouping the analyte in a probe volume,the probe volume being at least one pre-set spatial region, contactingmagnetic particles with the analyte to attach the magnetic particlesthereto either before or after the step of grouping the analyte,exposing the magnetic particles attached to the analyte to a magneticfield, recording a signal due to the magnetic induction produced by themagnetic particles as a result of their exposure to the magnetic field,generating quantitative data on the content of the analyte in themixture being analysed from the value of the signal, wherein themagnetic field has a spectrum, and the spectrum is pre-set with spectralcomponents at least at two frequencies, wherein the amplitude of atleast one of the spectral components is chosen high enough to ensure anon-linear dependence of the magnetic induction on the strength of themagnetic field, and the signal is recorded at such a frequency that is alinear combination of the frequencies of the spectral components duringthe exposure of the magnetic particles to the magnetic field.
 57. Themethod as defined in claim 56, wherein magnetic field strength vectorspertaining to the at least two spectral components are orientednon-collinear to each other.
 58. The method as defined in claim 56,wherein the magnetic particles are attached to the analyte through anintermediate material.